In recent years, in order to enhance visibility of image display devices, a gap between an image display panel such as a liquid crystal display (LCD), a plasma display (PDP), or an electroluminescence display (ELD) and a protective panel or a touch panel member disposed on the front side (viewing side) thereof has been filled with a resin such as an adhesive or a bond to suppress reflection of incident light or light emitting from the display image at an air layer interface.
For example, Patent Document 1 discloses, as a method for producing an image display device constituent laminate having a constitution in which image display device constituent members are laminated on at least one side of a transparent double-sided adhesive sheet, a method including bonding an adhesive sheet subjected to primary crosslinking by UV light to the image display device constituent members, and thereafter irradiating the adhesive sheet by UV light with the image display device constituent members interposed for secondary curing.
When the image display device constituent members are bonded into a single body by the adhesive material as described above, a positional shift or a work error involving air bubbles or foreign substances between the members may occur at the time of bonding work. Thus, the adhesive sheet is required to be repeeled in order to correct this error. Accordingly, there is a case in which the adhesive material used for such a purpose is required to exhibit repeelability (reworkability). In particular, for a laminate made of plate-shaped members having no flexibility, it is not easy to separate after once being bonded. Therefore, when a member for a large screen having difficulty in bonding or an expensive member is bonded, an adhesive material having reworkability has been required.
Conventionally, as the adhesive material having repeelability (reworkability), for instance, Patent Document 2 suggests an adhesive for optical films, which is used a specific acrylic triblock copolymer, and which has excellent adhesion properties and durability without chemical crosslinking, wherein the films can be removed with appropriate peeling strength without adhesive transfer, as a suitable adhesive for the image display devices.
In addition, as a double-sided adhesive sheet which is constituted so as to be repeelable from at least either one of the touch panel or the display surface of the display device, and which is characterized by having optical isotropy, Patent Document 3 discloses a repeelable constitution which is exhibited by having smaller adhesiveness of an adhesive layer on a display device side against a display surface of a display device compared to adhesiveness of an adhesive layer on a touch panel side against a bonding surface of a touch panel.
Further, Patent Document 4 discloses an adhesive sheet which is constituted to have a detachable interface (“internal detachment interface”) therein, which is different from bonding surfaces of the adhesive material with the adherends, as a repeelable adhesive material.